The drilling of boreholes with a rotary drilling rig requires that a drill bit be attached to or removed from the end of a tubing string from time to time. Drill bits are extremely heavy and difficult for roughnecks to handle. Usually one or more people are required for the difficult task of manually screwing the bit onto or off of the end of the tubing string.
It has been proposed to use a bit breaker wherein a plate member is apertured and provided with lugs for engagement with the external flow passageways formed exteriorly of a bit. However, such a tool is dangerous to use in proximity of the borehole for the reason that the bit could inadvertently be dropped to the bottom of the wellbore. This is a catastrophic event in the oil field and calls for an expensive fishing job to be carried out by experts.
It would, therefore, be desirable to have made available a tool which could be placed in the rotary table, and within which the drill bit could be safely seated in such a manner that the bit is precluded from falling into the borehole, and at the same time, the bit is controllably rotated in either direction. Such a novel and desirable combination of apparatus would enable the bit to be made up and broke out respective to the drill tubing in a safe and reliable manner. Moreover, it would be convenient if a removal handle could be attached to the bit in a manner which would enable the bit to be lifted and manipulated by two people. Such a desirable combination is also the subject of the present invention.